821421 has 10 divisors (see below), whose sum is σ = 1227182. Its totient is φ = 547560.

The previous prime is 821411. The next prime is 821441. The reversal of 821421 is 124128.

It can be written as a sum of positive squares in only one way, i.e., 585225 + 236196 = 765^2 + 486^2 .

It is not a de Polignac number, because 821421 - 2⁹ = 820909 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 821394 and 821403.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (821411) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 4990 + ... + 5151.

2⁸²¹⁴²¹ is an apocalyptic number.

821421 is a gapful number since it is divisible by the number (81) formed by its first and last digit.

It is an amenable number.

821421 is a deficient number, since it is larger than the sum of its proper divisors (405761).

821421 is a wasteful number, since it uses less digits than its factorization.

821421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10153 (or 10144 counting only the distinct ones).

The product of its digits is 128, while the sum is 18.

The square root of 821421 is about 906.3227901802. The cubic root of 821421 is about 93.6530517790.

Adding to 821421 its reverse (124128), we get a palindrome (945549).

The spelling of 821421 in words is "eight hundred twenty-one thousand, four hundred twenty-one".